Halogen-free flameproofed PC/ABS molding compositions are generally known.
Thus for example, flameproofed PC/ABS compositions that contain low-volatility oligomeric phosphoric acid esters as flame-retardant additive are described in U.S. Pat. No. 5,204,394. The molding compositions are characterized by a good thermal shape stability of molded bodies and flow line strength, and with a wall thicknesses of 1.6 mm have a V-0 rating in the UL 94 V flame resistance test. However, such a rating is not sufficient for many thin-wall applications. In order to achieve a satisfactory flame resistance also with thinner wall thicknesses, relatively large amounts of the plasticizing flame-retardant additive have to be added. Such molding compositions have an inadequate thermal shape stability and tend to form burning droplets in the aforementioned flame test, with the result that they achieve only a V-2 rating in the UL 94 V test.
In U.S. Pat. No. 5,849,827, it is disclosed that the afterburning times of PC/ABS molding compositions containing flameproofing agents can be reduced by adding nanoscale inorganic materials. The tendency to form burning droplets, especially in the case of thin wall thicknesses is, however, unaffected thereby.
PC/ABS compositions that contain silicate minerals are also known.
These reinforcing minerals may be used in order to obtain a very wide range of effects. They are used for example in order to have a positive effect on the stiffness and dimensional stability of the compositions. EP-A 0 391 413 describes PC/ABS molding compositions reinforced with platelet-shaped inorganic fillers, which are characterized by a low coefficient of thermal expansion as well as by a good toughness and thermal stability. U.S. Pat. No. 5,965,655 describes PC/ABS compositions to which special wollastonites are added in order to reduce the coefficient of thermal expansion, and which are characterized by an improved surface appearance combined with a good impact resistance. EP-A 0 452 788 describes PC/ABS molding compositions to which talcum is added in order to reduce the degree of surface gloss. WO 98/51737 describes PC/ABS compositions containing mineral fillers such as talcum and wollastonite that have improved thermal stability, melt flowability, dimensional stability and low-temperature toughness. EP-A 1 038 920 describes inter alia PC/ABS molding compositions reinforced with talcum and wollastonites that have an improved stability to hydrolysis. However, all these molding compositions are not flameproofed molding compositions, and are thus materials that do not pass the UL 94 V test.
Flameproofed PC/ABS molding compositions containing silicate minerals are also known.
PC/ABS molding compositions containing platelet-shaped minerals such as talcum and which are flameproofed with readily volatile monophosphates or halogen-containing additives are described in EP-A 0 641 827. Although the aforedescribed molding compositions have a high modulus of elasticity, they have an insufficient toughness and flow line strength for many thin-wall housing applications.
EP-A 0 754 531 describes PC/ABS molding compositions flameproofed with special low-volatility oligophosphates that contain platelet-shaped fillers such as layer-type aluminosilicates and are characterized by improved dimensional stability. In order to achieve these desired effects, comparatively large amounts of fillers are necessary, whereby a toughness of the molding compositions sufficient for thin-wall applications is no longer ensured.
In WO 00/46298 mixtures of polycarbonate and rubber-modified styrene resins are described that have been flameproofed with phosphoric acid esters and that contain talcum in low concentrations. The described molding compositions are characterized by improved resistance to hydrolysis, but do not satisfy the stringent flameproofing requirements that thin-wall housing applications have to meet. PC/ABS molding compositions are also described in WO 00/46298. These, however, are based on readily volatile monophosphates as flame-retardant additives and do not exhibit a satisfactory processing behavior in injection molding.
EP-A 1 026 205 describes flameproofed PC/ABS compositions containing silicate materials such as talcum or wollastonite that are also characterized by improved hydrolysis behavior but insufficient flame resistance for thin-wall applications.
WO 00/39210 also describes reinforced PC/ABS compositions having an improved resistance to hydrolysis, that have been flameproofed with special phosphoric acid esters having a low acid number. Talcum or mixtures of talcum and glass fibres among other substances may be used as reinforcing material. The described molding compositions have an insufficient toughness.
JP-A 11 199 768 describes PC/ABS compositions with phosphoric acid esters as flameproofing additives and that contain inorganic fillers such as talcum. The molding compositions are characterized by an excellent flame resistance (UL 94 V-0 rating for wall thicknesses ≦1.0 mm) as well as by a good thermal stability and notch-impact resistance. These molding compositions have an unsatisfactory processing behavior however.
The flameproofed PC/ABS molding compositions described in WO 01/48074 containing particularly pure talcum are characterized by improved stress-crack behavior, high rigidity and good flame resistance. However, they do not satisfy the stringent requirements in regard to the processing behavior (avoidance of tool plate outs), thermal stability as well as toughness and flow line strength of many thin-wall housing applications.